Linerless labels, such as shown in U.S. Pat. No. 3,051,588, 3,285,771, and 4,851,383, and in Canadian patent 1,248,412, are known to have advantages over conventional pressure sensitive labels which are mounted on a liner having a release coating. In conventional labels, the liner acts as a support for transport, printing and storage, and is discarded after the label is removed from the liner. In contrast, a linerless label has a face surface coated with a release coating and a back surface that is coated with a pressure sensitive adhesive (PSA). A strip of linerless labels may be wound in a roll configuration so that the PSA on the back side of the strip is in contact with the release coating on the face side of the strip, where the release coating faces outwardly. The adhesion between the PSA and release coating hold the strip in a roll. Labels can be peeled off individually from the roll of linerless labels, without having a liner web to tear off and discard each time a label is used.
Because a liner web is not needed in a roll of linerless labels, certain advantages and cost savings have been achieved including substantial material reduction due to the lack of a liner, elimination of the disposal liner and costs associated with release coated liners, and space savings in that approximately a roll of linerless labels can have about twice as many labels as a same size roll of liners with labels. Despite these advantages, linerless labels have not enjoyed had widespread commercial acceptance. The lack of acceptance is perhaps due in part to impediments to easy and clean peeling of the PSA from the release coating in the roll format. For example, if the adhesion between the PSA and the label substrate is weak or becomes weak (adhesion strength degrades over time under some environmental conditions and materials), then the PSA adhesive may stick to the release coating instead of the label as is intended, or the substrate may be tom when the labels are peeled off the label roll.
According to the present invention, a linerless label stock, and a method of making linerless labels, are provided which enhance the viability of linerless labels by providing a more secure adhesion of the PSA to the substrate than is typically provided in the prior art. According to the present invention a tie coat is provided which facilitates adherence of the PSA to a first face (the "back") of the substrate, the tie coat adhering to both the substrate first face and the PSA. The tie coat preferably comprises a dispersion of a pigment such as silica, with a binder, such as PVA. For example, the tie coat may consist essentially of about 30-40 parts silica dispersion, about 20-35 parts PVA, and about 30-40 water. Printing may be provided on the substrate first face, or may be applied onto the release coating by certain printing techniques.
According to the method of making linerless labels of the invention, a coating machine is utilized with a substrate having first and second faces. The method comprises the steps of: (a) Continuously moving the substrate in a first direction through the coating machine, and substantially sequentially: (b) With the coating machine, applying in a predetermined sequence to the moving substrate a tie coating to the substrate first face, a release coating to the substrate second face, and a pressure sensitive adhesive to the tie coating. (c) Cutting the substrate to form individual labels. And, (d) rolling the substrate into a roll, with the release coated second face on the outside of the roll. In the practice of the method set forth above, the predetermined sequence of step (b) is preferably to apply the tie coating first, then the release coating, and then the pressure sensitive adhesive. The cutting step may be die cutting, and drying at a rate much faster than ambient air drying may be practiced before steps (c) and (d), by hot air, infrared, or like drying technique.
It is the primary object of the present invention to provide an advantageous linerless label stock, and a simple yet effective method for making the stock. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.